A typical light emitting diode driver outputs constant current for loads of one or more light emitting diodes of an LED lamp. An LED lamp may be connected to a light emitting diode driver, such as in a North American Linear troffer fixture. In a light emitting diode retrofit system, an LED lamp composed of light emitting diodes in parallel and/or series may be driven with direct current (DC) using an LED driver with DC output. Multiple LED lamps can be driven in parallel, and when any LED lamp is removed the remaining LED lamps share the total current. As an example, when three LED lamps are driven at 6 Amperes and one of the LED lamps is removed, the remaining two LED lamps still share the 6 Amperes. Increasing the current to the remaining lamp increases the light of the remaining lamp and reduces its lifetime.
With reference top US 2015/0195884, EP1889519, EP2814302, US2008/0297062, and US2011/0210675, several solution are known for setting athe current of a driver. All these solutions propose to have an additional element in the lamp for identifying on the driver side the number of connected lamp. In particular, it is possible to add a resistor inside each lamp and to have one or two specific output(s) that could be provided in parallel to corresponding input of the driver in such a way that the driver set his power as a function of the measured equivalent resistor. Such solution needs to pair the drivers and the lamp and does not enable to adapt the power of the driver when a lamp fails.